1. which: who.

3-4. In whose confine immured is the store / Which should example where your equal grew: i.e., within whom is contained the resources which would be required to produce another you equal to the original.

5-6. Lean penury within that pen doth dwell / That to his subject lends not some small glory: It is a very poor poet who does not confer some honor upon the subject of his poetry.

10. clear: glorious.

11. counterpart: copy.   fame: make famous.

13. curse: an ill quality (in your own character).

14. Being fond: doting.   makes your praises worse: diminishes the praise due you.